Electrical apparatus including a pair of replica impedances for measuring distances along a loaded electrical line



Oct. 29, 1968 HOEL 3,408,564

ELECTRICAL APPARATUS INCLUDING A PAIR OF REPLICA IMPEDANCES FORMEASURING DISTANCES ALONG A LOADED ELECTRICAL LINE Filed Feb. 1, 1965REACTANCE FIG. 1

OR RA A EsEFArEF ELECTRONIC COUNTER United States Patent DISTANCES ALONGA LOADED ELECTRICAL LINE Hans Hoel, Oslo, Norway, assignor to TheEnglish Electric Company Limited, London, England, a British companyFiled Feb. 1, 1965, Ser. No. 429,216 priority, application GreatBritain, Feb. 5, 1964,

4,863/64 5 Claims. (Cl. 324-52) Claims invention relates to electricalapparatus for measuring the line, and more which the load point is anearth fault aflecting an electrical power supply line. From one aspect,apparatus pendent on the distance measurement.

It is to be understood, however, that the invention is not necessarilylimited to power lines and fault distance be described, by Way ofexample, with reference to an accompanying drawing in which:

FIG. 1 shows graphically an impedance diagram 1llustrating the impedancevectors of the power line and various components of the apparatus; and

3,408,564 Patented Oct. 29, 1968 FIG. 2 shows a circuit diagram of theapparatus according to this invention.

Referring now to the drawings, in FIG.

when the'phase angle is In FIGURE 2, the apparatus includes thetransformers 11 and 12 having primary windings 13 and 14, respectively,which are connected in series across input terminals 15, and furtherprimary windings 16 and 17 of these transformers are connected inparallel across input terminals 18 which, in turn, are in series withpotentiometers 19 and 20.

A phase comparator 21 has input terminals 22 23 coupled to secondarywindings 24 and 25 of the two 21 and an electronic counter 27.

line applied to input terminals 21 is arranged to measure the thusrepresenting the impedance vectors (R Z) and (R -f-Z). The resultingoutput signal from the phase then protective action may be It is to beunderstood that to the particular arrangement described and illustrated.

and magnitudes or angular positions in-line with the vector Z.

Furthermore, the phase comparator may be arranged instead to measure thephase angle between the vectors 3 R and (R Z). This modification howeverhas a disadvantage in so far as the measurement of phase angle is nowmuch more dependent on the value of the arc resistance occurring duringan electrical fault, thus rendering the distance measurements lessaccurate than before. In addition, although an electronic counter hasbeen described as the output device, a capacitor may alternatively beused, charged by the output from the phase comparator, so that theresultant voltage across this capacitor becomes a measure of thedistance to the electrical earth fault on the line. This arrangementwould be advantageous where several power lines, at a sub-station forexample, incorporate such an electrical apparatus, so that anelectrostatic voltmeter may be used to measure the resultant voltageassociated with each power line.

What I claim as my invention and desire to secure by Letters Patent is:

1. Apparatus for measuring from a reference datum the distance to a loadpoint along an electrical line having a predetermined load locus on anR-X operating characteristic of said apparatus, comprising a pair ofreplica impedances defining predetermined impedance vectors intersectingthe said datum on the characteristic, means for monitoring the currentand voltage of the line and applying one of these quantities to saidreplica impedances, means for deriving from the monitored quantities twolike vectorial components each dependent on said impedance vector and atleast one of which is dependent also on the ratio of the monitoredvoltage and current signals in a manner such as to intersect the loadlocus at said load point, and a phase comparator for determining thephase difierence between the two components whereby to derive therefroma measurement of the said distance.

2. Apparatus according to claim 1, wherein the two vectorial quantitiesare each dependent on both the said impedance vector and the ratio ofthe monitored voltage and current signals.

3. Apparatus according to claim 2, wherein the reference datum is theorigin of the operating characteristic and the impedance vector ispurely resistive.

4. Apparatus according to claim 3, wherein the two like vectorialquantities are currents, one being dependent on the sum of the resistivevector extending from one side of said origin and the ratio of themonitored voltage and current signals and the other being dependent onthe difference between the resistive vector extending from the oppositeside of the origin and the said ratio.

5. Apparatus according to claim 1, wherein the load locus ispredetermined for earth faults in an electrical power supply line.

No references cited.

RUDOLPH V. ROLINEC, Primary Examiner. G. R. STRECKER, AssistantExaminer.

1. APPARATUS FOR MEASURING FROM A REFERENCE DATUM THE DISTANCE TO A LOADPOINT ALONG AN ELECTRICAL LINE HAVING A PREDETERMINED LOAD LOCUS ON ANR-X OPERATING CHARACTERISTIC OF SAID APPARATUS, COMPRISING A PAIR OFREPLICA IMPEDANCES DEFINING PREDETERMINED IMPEDANCE VECTORS INTERSECTINGTHE SAID DATUM ON THE CHARACTERISTIC, MEANS FOR MONITORING THE CURRENTAND VOLTAGE OF THE LINE AND APPLYING ONE OF THESE QUANTITIES TO SAIDREPLICA IMPEDANCES, MEANS FOR DERIVING FROM THE MONITORED QUANTITIES TWO